Integrating 15S and 16S LiFePO4 Batteries in a Solar Setup

[raybies]

Hi everyone,

I’m currently running a 48V solar system and need advice on efficiently integrating two LiFePO4 batteries with different configurations:

1. Battery 1: 15S (48V nominal, 54.75V max) 50Ah
2. Battery 2: 16S (51.2V nominal, 58.4V max) 50Ah

Here’s the setup:

• I have a PV array charging through an MPPT controller in my inverter.
• The inverter runs at 48V but can only use one battery at a time due to the different voltage profiles of the 15S and 16S batteries.
• Neither battery has enough capacity to keep the inverter running through the night, so the system shuts down before sunrise, and I have to manually restart it.

Challenges:

• I can’t parallel these batteries directly because of their different voltages.
• I want to avoid over-discharging the lower-voltage 15S battery or undercharging the higher-voltage 16S battery.
• I also need a solution that allows both batteries to charge efficiently without manual intervention.

Questions for the Community:

• Has anyone successfully integrated 15S and 16S batteries in a similar setup?
• Any options apart from reconfiguring the 16S to 15S?

My goal is to minimize cost, maximize battery utilization and prevent manual intervention while ensuring safe operation.

Looking forward to your thoughts!

Thanks,

 

[sunshine_eggo]

• I can’t parallel these batteries directly because of their different voltages.

Correct.

• Has anyone successfully integrated 15S and 16S batteries in a similar setup?

No.

• Any options apart from reconfiguring the 16S to 15S?

Yes. Add a cell to the 15S? In both cases, you likely need to replace the BMS.

My goal is to minimize cost, maximize battery utilization and prevent manual intervention while ensuring safe operation.

Then you must commit to two 15S batteries in parallel or two 16S batteries in parallel.